"Preliminarily, we believe Mr. Smith acted alone. We don't believe it was a professional hit," Beverly Hills Police Chief David Snowden said.

Despite coverage that has speculated Chasen was killed as part of an elaborate plot, police now believe Smith, 43, an ex-convict, simply rode a bicycle alongside Chasen's Mercedes Benz and opened fire as she waited to make a left turn off Sunset Boulevard.

"We believe it was a random act, and we believe Mrs. Chasen was going to be the victim of a robbery," Beverly Hills Police Sgt. Mike Publicker said.

Chasen, 64, represented A-list movie stars and promoted some of Hollywood's top films. She was on her way home from the premiere of "Burlesque" on the night of Nov. 16 when she was killed.

Andrew Blankstein, a reporter for the Los Angeles Times, said that the Beverly Hills Police Department remains cautious despite what seems to be a break in the case.

"They're not saying that this is a closed case, and one of things that they're going to be looking … for is additional forensic material at the scene, as well as, one of the things that we've heard is that they were examining videotaped surveillance from the neighborhood. So does that surveillance show Mr. Smith either around the crime scene or on his way to the crime scene on his bicycle," Blankstein said.

Skeptics who have followed the case closely might find it hard to believe that one man on a bicycle could carry out this killing.

"There's been a lot of rumor built on rumor in this case and certainly with the speculation about theories of motive that's one of the aspects of this case which kind of definitely muddied the waters," Blankstein said. "In this kind of vacuum of information, people have come up with every kind of theory. I mean it's worthy of any kind of Hollywood plot line that you can come up with."

It turned out not be an elaborate, movielike plot, but information from a tipster to the TV show "America's Most Wanted" helped crack the case. Police sought to question Smith at his home in Hollywood's Harvey Apartments Dec. 1, after receiving an anonymous tip from "America's Most Wanted." Before they could talk to Smith, he shot himself to death.

"The tipster, at this point, wants to remain anonymous," Publicker said, "and we're going to respect that, as will "America's Most Wanted."

There was a reward of more than $100,000 for tips, and police say there is a possibility the person who called in the tip will get the reward.

The suspect, Smith, boasted about committing the murder, claimed he had $10,000 coming to him for the crime and said he would not be willing to return to jail, his neighbors told ABC News.

Smith had a long criminal record.

In the aftermath of his suicide, residents said they doubted Smith when he took credit for Chasen's murder. They noted that he was tall but of slight, unimposing build, and that he was seen regularly riding through the neighborhood on a bicycle, wearing gray gardening gloves and sometimes behaving strangely.

One neighbor of Smith's still doubts his involvement in the crime.

"It doesn't quite add up, that this would be somebody that would be able to do this by himself," Sammy Samorano said.

Beverly Hills police said Los Angeles investigators removed a bicycle from the scene of Smith's suicide and would be delivering it to the police for analysis.

Beverly Hills police repeatedly emphasized that the ballistics matching the guns were preliminary and that the investigation continues.

Suspect In Chasen Murder Was at Desperate Point in His Life

Previous reporting on the killing has suggested it was the work of an expert assassin. Today, police had another theory.

"We do not believe that he was a paid hit man," Publicker said.

"This was a random act of violence," he said. "With Mr. Smith's background, we believe it was most likely a robbery gone bad, at this time.

"Through the interviews and the information we received," Publicker said, "that leads us to believe that he was at a desperate point in his life, and was reaching out and doing desperate measures."

Earlier reports that ballistics had failed to link the guns in the two crimes also were incorrect.